Lüzhijiang Bridge on the Yuxi to Chuxiong Expressway in Yunnan

Project Overview:

The Lüzhujiang Bridge, located in Yimen County, Yunnan Province, China, is hailed as an engineering marvel perched on a sheer cliff face. It is the world’s first single-tower steel-box-girder suspension bridge, with a main span of 780 meters. Spanning the breathtakingly scenic Lüzhujiang Gorge, which boasts rich biodiversity, the bridge serves as a natural habitat for numerous wild animals, including the green peacock. Constrained by the elevation differences between the towns connected by the bridge, the bridge’s axis passes through the middle of the deeply incised gorge. Faced with a cliff terrain that rises to a height of 650 meters and features a natural slope of approximately 80 degrees, the designers pioneered a novel single-tower suspension bridge structure. The main cables, after passing over the top of the eastern tower, span the gorge in a single arc and are anchored into the solid rock of the western cliff face. The stiffening girders extend into segmented tunnels carved into the mountain, enabling zero excavation within the mountain itself. This ingeniously designed single-tower suspension bridge reduces the main span by 435 meters compared to traditional designs that circumvent the cliffs. By doing so, it not only saves about 500 million yuan in investment but also safeguards the gorge’s natural landscape and its rich biodiversity.

The Lüzhijiang Bridge project is fundamentally rooted in the integration of environmental and functional requirements. Its pioneering single-tower suspension bridge structure is both elegant and unique, achieving a perfect harmony between the engineering design and the ecological environment. This remarkable feat has created a bridge marvel perched on sheer cliffs, marking a significant advancement in bridge construction technology for mountainous canyon regions. Completed and opened to traffic in August 2022, the bridge has greatly improved transportation conditions in remote areas, boosted economic development in local ethnic minority regions, and has become a landmark architectural icon of the region.

Project Highlights:

The Creative Optimal Solution—The Single-Tower Suspension Bridge Design

Located on the southwestern border of China, the bridge site is situated in a deeply incised canyon with extremely rugged terrain. Constrained by the elevation differences between the villages and towns on either bank, the optimal elevation for the bridge deck of the Luzhijiang Bridge is approximately 1569.337 meters—precisely passing through the middle of the deep canyon. Faced with steep terrain featuring a height of 650 meters and natural slopes ranging from 70° to 80°, the bridge design abandoned the conventional twin-tower suspension bridge approach. Instead, the main cables are routed over the tower tops on the Yuxi side, then span the Luzhijiang Canyon in a single arch, pass through cable tunnels carved into sheer cliffs, and are supported and redirected by a novel composite cable saddle before being anchored securely within tunnel anchors embedded in the mountain. This innovative single-tower suspension bridge configuration breaks new ground in bridge construction across high-altitude, cliff-like terrains. Compared to an alternative route that would have bypassed the canyon through more open areas, this design reduces the main span by 435 meters and saves an investment of 500 million yuan.

Elegant Sustainability Solution—Zero Excavation for Slope Stabilization

As the monolithic steel box stiffening girder approaches the sheer cliff on the Chuxiong side, it splits into two sections, forming a “human” shape that extends approximately 18 meters into the main-line separated-tunnel structure. The split steel box stiffening girders are supported by the tunnel’s secondary lining. The bridge abutment and the tunnel’s secondary lining are integrated into a single structure, thereby eliminating the need to excavate 680,000 cubic meters of earth for the abutment slope. At the same time, this design accommodates the large displacement of 1.4 meters at the girder ends. In the section of the main cable near the Chuxiong-side mountain, within a 74.35-meter span, there are no suspenders. To address issues such as excessive deformation and vibration of the main girder and negative reaction forces at the girder-end bearings—especially given the special terrain conditions where it is impossible to install ground-anchor suspenders due to the sheer cliffs—a certain length of the box girder in this suspenders-free zone is equipped with concrete ballast blocks.

For the construction of tunnel anchors for suspension bridges, construction access roads are typically built on the front face of the mountain to reach the working area, after which the tunnel-anchor chambers are excavated. However, on the Chuxiong side, the mountain rises to a height of 650 meters, and its front face is sheer cliffs, making it impossible to build an access road directly to the tunnel-anchor excavation site. After on-site investigation, it was ultimately decided to adopt a detour strategy: first, the construction access road would be routed around the side and rear of the mountain; then, a horizontal construction adit would be excavated to penetrate deep into the mountain’s interior. From there, cable tunnels would be driven outward, while tunnel anchors would be excavated inward—thus realizing the “one tunnel leading to four caverns” scheme illustrated below. This approach achieved zero excavation on the slope, thereby maximizing the protection of the magnificent, pristine landforms and the rich wildlife and plant resources of the Lüzhijiang Gorge.

Outstanding Structure—New Maintenance-Free Composite Cable Saddles

Cable ducts are equipped with cable saddle piers. Based on the support, force transmission, and anchorage requirements of the main cables, the top of each pier features a sliding composite cable saddle that integrates both “main cable saddle” and “diverging cable saddle” functions. The saddle body serves to support the main cable, guide cable turning, and facilitate cable divergence. A set of rollers positioned beneath the saddle body enables longitudinal sliding of the saddle, thereby achieving horizontal force balance for the main cable and preventing cable strand slippage. Ultimately, this ensures smooth transfer of the main cable’s tension to the rear anchorages, meeting all the requirements of the bridge’s main cable redirection, strand dispersion anchorage, and strand anti-slippage performance. To address the durability needs of the core components of the composite cable saddle, this project has, for the first time, developed high-corrosion-resistant rollers. Specifically, the 12Cr13 stainless steel material has been applied to key load-bearing components of the bridge. Through heat treatment, the yield strength of this material has been increased by 45%, while its corrosion resistance is eight times greater than that of commonly used alloy structural steels, enabling maintenance-free operation throughout the entire service life. Coupled with a new installation technique, the flatness of the grating surface has reached 0.2 mm (compared to the code requirement of 0.5 mm), thus achieving highly precise installation.

Precision Protection—A Complete Set of Technologies for Preventing Rockfall Impacts on Bridges in Hazardous Mountainous Areas

Typically, bridge sites are chosen in broad, open sections of canyons. However, the west-bank deck of the Lüzhujiang Bridge pierces through the middle of the mountain slope, with a sheer, 320-meter-high cliff face above the bridge deck. Rockfalls from this steep cliff pose the primary threat to both the structural integrity of the bridge and driving safety. Consequently, the builders have attached great importance to preventing rockfalls from these extremely steep slopes. They conducted high-precision three-dimensional laser scanning and high-definition drone photography of the slope, meticulously inspecting key areas to determine the spatial distribution, interconnections, and interlocking conditions of rock joints on the slope surface. Based on these findings, they implemented a comprehensive, multi-layered slope protection system consisting of: localized removal of loose rock masses; point-specific, independent anchor cables for critical protection zones; active netting covering the entire slope surface; and segmented passive netting systems—ensuring complete, three-dimensional coverage of the slope and effectively mitigating the risk of large rock masses falling and impacting the bridge structure. At the same time, taking into account the existing slope protection measures, they identified the locations and volumes of potentially unstable, weathered rock fragments. By conducting dynamic simulation analyses, they determined the trajectories of these fragmented rocks and their impact forces on the bridge deck. As a result, they strategically installed high-energy-absorbing, flexible protective shelters specifically designed to withstand impacts, thereby preventing direct strikes by falling debris onto the bridge deck and passing vehicles, and ensuring both the structural integrity of the bridge and the safety of road users.

High-standard construction—efficient lifting at an altitude of 320 meters

A temporary fabrication plant for steel box girder segments was set up on an open space in a mountain valley. Once the segments were completed, they were lifted and installed using cable cranes. The height difference between the bridge deck and the steel beam lifting area at the valley bottom reached 320 meters—the highest lifting height in the world. Cable cranes, with a rated lifting capacity of 180 tons, served as the primary lifting equipment for erecting the steel beams. A total of 20 main cables were installed, along with two overhead traveling cranes. The traction and lifting winches employed 22-ton friction-type winches, each with a rope capacity of up to 3,300 meters. The project also developed a multipurpose lightweight lifting device suitable for both monolithic and segmental steel box girders. The connection between the lifting device and the steel beam adopts a tension-compression force transmission mode, fully leveraging the steel beam’s inherent lateral bending resistance. This design makes the lifting device lightweight and highly flexible, enabling efficient installation of three standard segments per day.

Honored Achievements:

FIDIC Global Infrastructure Excellence Award;
IABSE “Best Construction Innovation Nomination Award”;
China Highway Society Bridge Engineering Innovation Award;
China Highway Society “Tunnel and Underground Space Innovation Engineering” Award;
Holds 11 patents, has published 21 papers, and has developed 3 provincial- and ministerial-level construction methods.

Project Showcase: